1. Technical Field
The present invention relates to a method to control data flow rate of data transmitted over a connection set up between a source terminal and a destination terminal via a plurality of network links and network nodes at least one of which constitutes a queuing network node which is able to return data flow control packets to the source terminal, the data flow control packets containing information based on which the data flow rate is to be controlled in the source terminal, a queuing network node wherein the method is performed, and a packet switching network including such a queuing network node
2. Description of Related Art
Such a method, queuing network node and packet switching network are already known in the art, e.g. from the international application published under the Patent Cooperation Treaty (PCT) with reference number WO 93/2063 and with title `Congestion Control For Cell Networks`. Therein, a packet switching network named a cell switching communication network is described wherein so called source nodes transmit data packets to so called destination nodes via network nodes and network lines. Such a network node can be provided with a buffer, in which case it performs the role of a queuing point for bursty traffic that is rather delay insensitive. In such a queuing point, the state of congestion is determined by monitoring the buffer filling level and when congestion is expected, feedback data flow control packets constituting a so called feedback rate control signal, are sent from the queuing point to the source nodes. Upon receipt thereof, a source node adapts its transmit rate. More specifically, the queuing points in the known network return two bit codewords to the source nodes when congestion is expected to make these source nodes either decrease, quickly decrease, remain constant or increase their transmit rates. Since it is not checked anywhere in the network how a source node has adapted its transmit rate, the known network relies upon fair behavior of the source nodes. These sources however may increase their transmission rates in a fraudulent way thereby increasing the probability for buffer overflow and data loss in the packet switching network. In a transmission class such as the Available Bit Rate (ABR) class defined by the ATM Forum in the draft Standard with reference ATM Forum.backslash.95-0013R10, source nodes are supposed to increase their transmit rates exponentially. If however some of the sources increase their transmit rates stepwise instead of exponentially, queuing points in the network may get overloaded and consequently the network may fail to observe the traffic contracts made up between ABR subscribers and the network operator.